1. Field of the Invention
The present invention generally relates to miniature switches for electrical and electronic apparatus and, more particularly, to miniature switches suitable for mounting with electronic apparatus in an electrical switch cover plate to monitor actuation of electrical switches.
2. Description of the Prior Art
It has recently been proposed to provide a voice recording device in an electrical wall switch plate, such as is disclosed and claimed in U.S. patent application Ser. No. 08/685,609, filed Jul. 24, 1996, of which the present inventor is a joint inventor and which application is hereby fully incorporated by reference as if the text thereof were fully set forth herein. In this combination, it is contemplated that the actuation of the wall switch should cause the playback of an audio message of one or more messages (possibly of a sequence of messages) that may be recorded at will, preferably by recording samples of the message in random access memory or other solid state memories.
Such recordation has been facilitated by recent reductions in cost of relatively large capacity semiconductor memories and integrated circuits capable of conversion of analog signals to digital signals and vice-versa. Thus, it is possible to provide the necessary electronics, including a speaker, microphone and battery power supply within a wall switch plate cover with only a relatively modest increase in the thickness thereof (e.g. about a 7/16 inch overall thickness, increasing thickness over a conventional switch plate generally by less than 1/4 inch).
However, providing sensing of operation of a wall switch as desired for this application within a switch plate cover is not trivial. The existing wall switch provides the mounting arrangement for the switch plate and conventional switch plates are designed to be drawn tightly against the body of the wall switch with virtually the entirety of the actuating lever of the wall switch protruding therethrough. Of course, external mechanisms would be unsightly and potentially dangerous.
Current sensing in the controlled circuit is less than fully reliable due to possible variation or disconnection of the load controlled by the switch and, in any event, it is desirable for purposes of simplicity and safety of installation of the device to retrofit it to an existing wiring system without disturbance of existing wiring in any way. Prevailing electrical codes may prohibit and restrict any incursion of any portion of the device or its circuitry into an existing electrical wiring box.
Accordingly, the above-incorporated U.S. Pat. No. 5,871,086 is directed to switch structures and actuating linkages therefor which are very thin and provide a momentary contact connection as an electrical switch lever is moved through a position intermediate between extreme positions. However, it is often the case that several electrical switches will be provided together in the electrical system of a building in which such a device will be desired and the device activated upon the actuation of any of two or more electrical switches. In such a case, the linkages and switches can be provided for any or all switches which are ganged together in a single electrical box and the switches connected in parallel so that actuation of any electrical switch for which a linkage and momentary contact switch is provided will actuate the device.
However, such an arrangement is less than optimally efficient for manufacture. Further, while the switch structures disclosed in the above-incorporated U.S. Pat. No. 5,871,086 are highly reliable, difference in frequency of actuation of the electrical switches may cause different levels of wear. Additionally, near simultaneous actuations of two or more switches may result in multiple control signals for the device which may result in malfunction or an undesired restarting of operation. Further, the contacts of such switches may be exposed to ambient gases and/or particulate matter in the atmosphere and within the electrical installation which may cause fouling, oxidation and/or corrosion of the contacts.